Issues in resistance, adherence, and comparative efficacy of the single-tablet regimen combination of tenofovir, emtricitabine, and efavirenz in the management of HIV-1 infection
Gabriel Rebick, Sharon L Walmsley
Division of Infectious Diseases, Department of Medicine, University Health Network, University of Toronto, Toronto, ON, Canada
Abstract: Atripla is the first once-daily, single-tablet, triple-combination antiretroviral therapy. It is recommended for the initial treatment of the naïve patient with human immunodeficiency virus-1 (HIV-1) infection in all current guidelines, based on its proven efficacy in numerous head-to-head randomized clinical trials. Not only has it proven efficacy, but the fixed-dose combination, Atripla, has resulted in an improvement in adherence, quality of life, and satisfaction among naïve as well as virally suppressed patients switching from another regimen. Despite the advantages, tolerability issues can arise that are related primarily to the efavirenz component, which is known to cause central nervous side effects such as dizziness, abnormal dreams, and anxiety. Although generally self-limited, these side-effects can lead to treatment discontinuation in the short- or long-term. Based on the observation of neural tube defects in macaque models, and isolated case reports in human fetuses with first trimester exposure, it is rated as Food and Drug Administration pregnancy category D, and considered as contraindicated in the first trimester of pregnancy where alternatives are available. Given the low genetic barrier of each of the individual components, resistance remains an important issue for patients with poor adherence, but is balanced in part by the long half-life of the drugs. Transmitted resistance is described in up to 16% of newly infected patients in population surveys, and is particularly prevalent in men who have sex with men. Minority variants that may impart resistant to efavirenz are not detected with currently used HIV-1 genotype assays, but nonetheless may also be implicated in patients who fail initial treatment. Several single-tablet regimens are recently licensed or in development that will challenge Atripla as the single-tablet first-line option, but none have shown superior efficacy to date.
Keywords: Atripla, adherence, HIV, resistance, fixed-dose, efavirenz
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